This supplement is needed to support a sufficient number of animal experiments in order to test the safety and efficacy of the techniques to be developed during this grant. Support for animal studies was originally to have come from NIH Contract N01-AM-5-2211 entitled "Endoscopic Control of Continuing Massive Gastric and Duodenal Bleeding in a General Hospital Population", but we have learned that further support for animal trials from this source will not be forthcoming during the second and third years of this grant (GM 25262). Successive prototypes of the high-powered Nd:YAG fiber photocoagulator and the automated thermal probe must be carefully tested in an adequate number of animals by: (1) application to intact normal gastric mucosa at laparotomy to determine optimal performance parameters; (2) use in laparotomy experiments to determine efficacy and safety in stopping bleeding from standard experimental gastric ulcers; and finally (3) determination of efficacy and safety in stopping bleeding from gastric ulcers with a single briskly bleeding artery at endoscopy. Only those prototypes which have proven safe and efficacious in the first two experiments will be studied endoscopically in the third final experiment. Depth of injury will be evaluated histologically at one week when injury is maximal.